High temperature vacuum creep forming fixture

ABSTRACT

A high temperature vacuum creep forming fixture is disclosed comprising a vacuum chamber, a die with heating electrodes therein for receiving a metallic blank, and a high heat resistant forming diaphragm for pressing the metallic blank over said hot die for forming the blank into the desired part, and for raising the diaphragm clear of the die. A new heat resistant diaphragm per se, is disclosed comprising a plurality of interconnected elongated modules of high heat resistant insulating material secured to a plurality of two sheets of heat resistant materials, one sheet being of aluminized asbestos cloth for reflecting the heat back and the other sheet or sheets being of fiberglass reinforced silicone rubber for providing high strength and flexibility in the diaphragm for forming and lifting a highly efficient heat insulating diaphragm. Alternatively, a ring spring may be placed over the diaphragm for urging the periphery thereof outwardly.

United States Patent 1 [111 3,739,617 Stejskal June 19, 1973 HIGH TEMPERATURE VACUUM CREEP FORMING FIXTURE [75] Inventor: Ladislav M. Stejskal, Seattle, Wash.

[73] Assignee: The Boeing Company, Seattle, Wash.

[22] Filed: Sept. 21, 1970 [21] Appl. No.: 73,927

[52] US. Cl. 72/63 [51] Int. Cl B21d 22/12 [58] Field of Search 72/54, 57,63;

18/DlG, 19; 29/421 [56] References Cited UNITED STATES PATENTS 2,348,921 5/1944 Pavlecka 72/63 2,423,862 7/1947 Vorobik 72/63 3,006,306 10/1961 Pfeiffer et al... 72/63 3,172,173 3/1965 Ellms 72/63 3,566,650 3/1971 Johnson... 72/63 3,593,551 7/1971 Roth 72/63 Primary Examiner-Richard J. Herbst Att0rney--Glenn Orlob and Theron H. Nichols A high temperature vacuum creep forming fixture is disclosed comprising a vacuum chamber, a die with heating electrodes therein for receiving a metallic blank, and a high heat resistant forming diaphragm for pressing the metallic blank over said hot die for forming the blank into the desired part, and for raising the diaphragm clear of the die. A new heat resistant diaphragm per se, is disclosed comprising a plurality of in terconnected elongated modules of high heat resistant insulating material secured to a plurality of two sheets of heat resistant materials, one sheet being of aluminized asbestos cloth for reflecting the heat back and the other sheet or sheets being of fiberglass reinforced silicone rubber for providing high strength and flexibility in the diaphragm for forming and lifting a highly efficient heat insulating diaphragm. Alternatively, a ring spring may be placed over the diaphragm for urging the periphery thereof outwardly.

ABSTRACT PATENIEB JUN 19 I975 mm 2 0r 4 INVENTOR. A/ID/SL/H M STEJSKAL SUMMARY OF THE INVENTION The disclosed invention pertains to a high tempera ture vacuum creep forming fixture comprising a die forming lower chamber portion and a diaphragm upper chamber portion.

The diaphragm upper chamber portion is illustrated as being mounted on rollers and tracks so that after the diaphragm has been raised subsequent to forming of a part, the diaphragm upper chamber portion is rolled back to provide clearance for removing the formed part and reloading the lower chamber portion with a new blank. Following positioning of the new blank over the die in the lower chamber portion, the diaphragm upper chamber portion is again moved over the lower chamber, lowered until into sealing engagement therewith and then the vacuum pulled from under the lower chamber to press the diaphragm on the blank to form it over the die.

The vacuum in this new vacuum creep forming fixture is controlled by valves in both the lower chamber portion and in the upper chamber portion for either forcing the blank down over the die with the diaphragm and for raising the diaphragm clear of the die for removing the newly formed part and inserting a new blank.

Likewise, a new diaphragm is disclosed for use in high temperature environments, such as but not limited to, for use in the disclosed new vacuum creep forming fixture. It comprises a layer of continuous, interconnected elongated modules made of aluminized asbestos cloth and alumina-silica fibers and cloth mounted on a sheet of fiberglass reinforced silicone rubber for providing strength, flexibility, and an air tight seal.

Two modifications of a diaphragm are disclosed, one utilizing two preformed fiberglass reinforced silicone rubber corners on each side of the diaphragm and the other diaphragm utilizing a flexible silicone rubber sheet on each side for distribution of stresses on the peripheral edges of the diaphragm,

Accordingly, a primary object of this invention is to provide a forming fixture that utilizes vacuum forces for actuating a diaphragm for pressing a blank over a die to the shape thereof in place of utilizing pneumatic, hydraulic, or mechanical actuating forces.

Another object of this invention is to provide a vacuum creep forming fixture that may be rapidly opened and closed even at very high temperatures.

A further object of this invention is to provide a high temperature heat resistant diaphragm.

Still another object of this invention is to provide a high heat resistant diaphragm comprising a layer of interconuected modules of heat resistant material.

A still further object of this invention is to provide a high heat resistant diaphragm comprising a layer of interconnected modules with the addition of two layers of high heat resistant material.

Other objects and various advantages of the disclosed high temperature vacuum creep formingfixture will be apparent from the following detailed description, together with the accompanying drawings, submitted for purposes of illustration only and not intended to define the scope of the invention, reference being made for that purpose to the subjoined claims.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings diagrammatically illustrate by way of example, not by way of limitation, two forms of the invention wherein like reference numerals designate corresponding parts in the several views in which:

FIG. I is a schematic perspective view of the high temperature vacuum creep forming fixture wherein the diaphragm upper chamber portion is illustrated as being rolled clear of the forming lower chamber portion;

FIG. 2 is a view similar to FIG. 1, except the upper and lower portions are illustrated as sealed together for forming;

FIG. 3 is a schematic sectional view of the high temperature vacuum creep forming fixture illustrating the diaphragm being lifted by the vacuum;

FIG. 4 is a view similar to FIG. 3, but with the diaphragm illustrated in forming position;

FIG. 5 is a schematic perspective view of a portion of the diaphragm upside down with parts broken away;

FIG. 6 is a detailed enlarged schematic view ofa por tion of FIG. 5;

FIG. 7 is a schematic sectional view of one of the in sulating modules and adjacent portions of the membrane, all upside down;

FIG. 8 is a detailed enlarged schematic view of a portion of FIG. 5 with parts cut away;

FIG. 9 is a schematic sectional view of a portion of FIG. 8;

FIG. 10 is a schematic sectional view of a portion of one embodiment of the diaphragm; and

FIG. 11 is a modification of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention, the scope of which being defined in the appended claims, is not limited in its application to the details of construction and arrangement of parts shown and described, since the invention is capable of other embodiments and of being practiced or carried out in various other ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

FIG. 1, a schematic perspective view of the high temperature vacuum creep forming fixture 10, illustrates the diaphragm upper chamber portion 12 rolled on tracks 13 clear of die forming lower chamber portion 11. In this position the finished or new formed part may be removed from lower chamber portion 11 and a new blank placed in position over a die (not shown) therein.

FIG. 2 illustrates the diaphragm upper chamber portion 12 sealed over the die forming lower chamber portion 11 for operation of the high temperature vacuum creep forming fixture 10.

FIG. 3, a cross section of the high temperature vacuum creep forming fixture 10, illustrates the lower chamber portion 11 comprising a blank 14 of titanium, for example, positioned over ceramic die 15 having heating elements 16 therein, and vacuum pump pipe outlet and release valve, 17 and 18 respectively, all mounted in die frame 19. This vacuum creep forming fixture is particularly adapted for forming blanks of titanium and other refractory metals and superalloys, as nickelchrome, stainless steel, etc.

Upper chamber portion 12 includes high heat resis tant and high strength diaphragm 20 comprising a high heat resistant die forming portion 21 and a more flexible, supporting, vacuum membrane portion 22 connecting the peripheral edge of the die forming thick portion 21 to the upper frame 23. Air outlet 24 to a vacuum pump (not shown) and vacuum releasing valve 25 are coordinated with similar outlet 17 and vacuum release valve 18 to control the vacua being pulled on both sides of the diaphragm alternately. Upper diaphragm frame 23 is pneumatically sealed to lower die frame 19 with annular silicone rubber, or the like, seal 26.

As shown in FIG. 3, the vacuum pulled in the upper chamber, as controlled by the appropriate valves, is causing the ambient air pressure to support the diaphragm in the illustrated raised position. Annular steel free-floating frame rod 41 tends to maintain the diaphragm high heat resistant die forming portion 21 stretched out in a generally horizontal attitude.

FIG. 4 illustrates the reversal in vacua with the vacuum being pulled in the lower chamber instead of the top chamber after the ceramic die 15 is heated to forming temperature. The force of the vacuum on the flexible diaphragm then forms the blank to the shape of the die for producing the high temperature vacuum creep formed article.

More details of the high temperature heat resistant diaphragm are revealed in the following detailed drawings.

FIG. illustrates a portion of the diaphragm 20 upside down, i.e., the hot side on top, with parts cut away for clarity of disclosure.

FIG. 6,-an enlarged view of a portion of the diaphragm of FIG. 5, illustrates details of the modules as module 27 for example. Here, the cover 28 and end cover 29 comprise nickelchrome wire reinforced alumina-silica fiber insulating cloth such as but not limited to Fiberfrax manufactured by The Carborundum Company, Niagara Falls, N.Y., for enclosing a filler 30 of alumina-silica fiber.

FIG. 7, a sectional view of one of the modules 27, illustrates the insulating cover 28 stretched over the filler 30 and secured to an aluminized asbestos cloth bottom strip 31 of the module and a supporting sheet 32 of fiberglass reinforced silicone rubber with silicone rubber fastening pin 33 inside of grommets. Each row of pins 33 with their attendant grommets, FIG. 7, fasten the adjacent sides of two modules to the supporting sheet 32 and an insulating rope 34 of nickelchrome wire reinforced alumina-silica fiber insulating material protect the pins from the high heat of metal forming. Thus, a damaged module may be replaced by removing only the fastening pin on each side of the damaged module, the module replaced, and then the pin replaced.

A second supporting sheet 21 is stretchable silicone rubber and is adhesively secured to spacer strips 36 which are, in turn, adhesively secured to the supporting sheet 32.

FIG. 8, a detailed view of a part of the diaphragm of FIG. 5, with the modules cut away, and on this part, a

portion of the first supporting sheet 32 is cut away for clarity of disclosure.

FIG. 9, a cross sectional view of a portion of FIG. 8, illustrates the two silicone rubber supporting sheets 21 and 32 interconnected with spacer strips 36 and locking the silicone rubber fastening pin 33 thereto. Sheet 32 is also fiberglass reinforced silicone rubber and sheet 21 is stretchable silicone rubber.

FIG. 10 is a schematic sectional view of the preferred embodiment of the diaphragm wherein diaphragm 20a has a fiberglass reinforced flexible membrane 22a attached to upper frame 23 and integral with flexible, supporting membrane 21a. Here, preformed fiberglass reinforced silicone rubber annular angular strip 37 is adhesively secured to the supporting membrane 22a so as to overlap and loosely fit on the corner 38 of the upper frame 23. Likewise, preformed fiberglass reinforced silicone rubber annular angular strip 39 is fastened, as by an adhesive or the like, to the corner 40 of the flexible, supporting membrane 22a where it joins the high heat resistant die forming portion 21a and where the tension forces of the membrane 22a are at right angles to the diaphragm portion 21a and which portion 21a forms a supporting sheet which is secured adhesively and/or with fastening pins 33 to aluminized asbestos module cloth bottom strip 31. Thus, with raising and lowering of the diaphragm 20a producing the flexing or bending and straightening or pulling of the diaphragm membrane 22a, the strip 37 fits loosely over frame corner 38 and the strip 39 reinforces membrane corner 40,.all for increasing the wear life of the diaphragm membrane.

FIG. 11, a modification of FIG. 10, illustrates schematically another embodiment 20b of the diaphragm comprising a stretchable silicone rubber membrane 21b extending from on top of the upper frame 23 inwardly into a loop and back around free-floating frame 41. Membrane 22b is integral with the silicone rubber supporting sheet portion 21b. Sheet portion 21b is adhesively secured to silicone rubber sheet 32 through interconnecting spacer strips 36. Sheet 32 is secured to aluminized asbestos bottom cloth 31 of module 27 with silicone rubber fastening pin 33. Therefore, with raising and lowering of the diaphragm 20b which produces flexing and straightening or stretching of the diaphragm membrane 22b, the large bend in the membrane merely bends with little, if any, rubbing on upper frame 23.

Accordingly, it will be seen that the present high tem perature vacuum creep forming fixture operates in a manner which meets each of the objects set forth hereinbefore.

While only two embodiments have been disclosed, it will be evident that various other modifications are possible in the arrangement and construction of the disclosed high temperature vacuum creep forming fixture without departing from the scope of the invention, and it is accordingly desired to comprehend within the purview of this invention such modifications as may be considered to fall within the scope of the appended claims.

I claim:

1. A high temperature vacuum creep forming fixture comprising: vacuum chamber means; diaphragm means secured at its outer edges so as to divide the vacuum chamber into an upper and lower chamber; a die enclosed in said lower chamber for receiving and heating a metallic blank; an insulating blanket comprising a plurality of interconnected elongated modules fastened to the lower surface of the diaphragm and extending substantially across the forming surface of the die for providing thermal protection of the diaphragm from the metallic blank; and said diaphragm being responsive to vacuum creating means in said upper chamber for raising itself and the insulating blanket attached thereto, from contact with the metallic blank.

2. A high temperature vacuum creep forming fixture as recited in claim 1 further including: a heavy metal bar frame positioned over the diaphragm for forcing the diaphragm outwardly to prevent bridging of the plurality of interconnected elongated modules during the vacuum raising of the diaphragm.

3. Apparatus for hot creep forming a sheet material workpiece having a relatively high melting point such as titanium, comprising: a housing having an upper and a lower portion; a die enclosed in the lower portion for receiving and heating the workpiece; a diaphragm secured at its outer edges to the upper portion so as to form an upper lifting vacuum chamber; modular insulators attached in abutment relation to the lower surface of the diaphragm for providing thermal protection to the diaphragm from the workpiece; and said diaphragm being responsive to vacuum creating means in the upper portion for raising itself and the modular insulators attached thereto from contact: with the workpiece.

4. Apparatus for hot creep forming a workpiece as recited in claim 3 further including: a frame loosely fitted inside the upper lifting vacuum chamber and posi tioned for free floating action on the upper surface of the diaphragm to force the diaphragm adjacent the workpiece to move outwardly and prevent bridging of the modular insulators during the lifting operation thereby eliminating the peeling action of the shear forces caused by pulling the diaphragm inwardly. 

1. A high temperature vacuum creep forming fixture comprising: vacuum chamber means; diaphragm means secured at its outer edges so as to divide the vacuum chamber into an upper and lower chamber; a die enclosed in said lower chamber for receiving and heating a metallic blank; an insulating blanket comprising a plurality of interconnected elongated modules fastened to the lower surface of the diaphragm and extending substantially across the forming surface of the die for providing thermal protection of the diaphragm from the metallic blank; and said diaphragm being responsive to vacuum creating means in said upper chamber for raising itself and the insulating blanket attached thereto, from contact with the metallic blank.
 2. A high temperature vacuum creep forming fixture as recited in claim 1 further including: a heavy metal bar frame positioned over the diaphragm for forcing the diaphragm outwardly to prevent bridging of the plurality of interconnected elongated modules during the vacuum raising of the diaphragm.
 3. Apparatus for hot creep forming a sheet material workpiece having a relatively high melting point such as titanium, comprising: a housing having an upper and a lower portion; a die enclosed in the lower portion for receiving and heating the workpiece; a diaphragm secured at its outer edges to the upper portion so as to form an upper lifting vacuum chamber; modular insulators attached in abutment relation to the lower surface of the diaphragm for providing thermal protection to the diaphragm from the workpiece; and said diaphragm being responsive to vacuum creating means in the upper portion for raising itself and the modular insulators attached thereto from contact with the workpiece.
 4. Apparatus for hot creep forming a workpiece as recited in claim 3 further including: a frame loosely fitted inside the upper lifting vacuum chamber and positioned for free floating action on the upper surface of the diaphragm to force the diaphragm adjacent the workpiece to move outwardly and prevent bridging of the mOdular insulators during the lifting operation thereby eliminating the peeling action of the shear forces caused by pulling the diaphragm inwardly. 